THE 6‐minute walk test and other endpoints in Duchenne muscular dystrophy: Longitudinal natural history observations over 48 weeks from a multicenter study
TL;DR: Findings confirm the clinical meaningfulness of the 6MWD as the most accepted primary clinical endpoint in ambulatory DMD trials.
Abstract: Introduction: Duchenne muscular dystrophy (DMD) subjects ≥5 years with nonsense mutations were followed for 48 weeks in a multicenter, randomized, double-blind, placebo-controlled trial of ataluren. Placebo arm data (N = 57) provided insight into the natural history of the 6-minute walk test (6MWT) and other endpoints. Methods: Evaluations performed every 6 weeks included the 6-minute walk distance (6MWD), timed function tests (TFTs), and quantitative strength using hand-held myometry. Results: Baseline age (≥7 years), 6MWD, and selected TFT performance are strong predictors of decline in ambulation (Δ6MWD) and time to 10% worsening in 6MWD. A baseline 6MWD of <350 meters was associated with greater functional decline, and loss of ambulation was only seen in those with baseline 6MWD <325 meters. Only 1 of 42 (2.3%) subjects able to stand from supine lost ambulation. Conclusion: Findings confirm the clinical meaningfulness of the 6MWD as the most accepted primary clinical endpoint in ambulatory DMD trials.
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Case Western Reserve University1, Newcastle University2, Research Triangle Park3, Seattle Children's4, Boston Children's Hospital5, Duke University6, University of Pittsburgh7, Children's Hospital of Eastern Ontario8, University of Rochester9, Centers for Disease Control and Prevention10, Children's Hospital of Philadelphia11, Johns Hopkins University12, University of Rochester Medical Center13
TL;DR: Care considerations for diagnosis of DMD and neuromuscular, rehabilitation, endocrine (growth, puberty, and adrenal insufficiency), and gastrointestinal (including nutrition and dysphagia) management are presented.
Abstract: Since the publication of the Duchenne muscular dystrophy (DMD) care considerations in 2010, multidisciplinary care of this severe, progressive neuromuscular disease has evolved. In conjunction with improved patient survival, a shift to more anticipatory diagnostic and therapeutic strategies has occurred, with a renewed focus on patient quality of life. In 2014, a steering committee of experts from a wide range of disciplines was established to update the 2010 DMD care considerations, with the goal of improving patient care. The new care considerations aim to address the needs of patients with prolonged survival, to provide guidance on advances in assessments and interventions, and to consider the implications of emerging genetic and molecular therapies for DMD. The committee identified 11 topics to be included in the update, eight of which were addressed in the original care considerations. The three new topics are primary care and emergency management, endocrine management, and transitions of care across the lifespan. In part 1 of this three-part update, we present care considerations for diagnosis of DMD and neuromuscular, rehabilitation, endocrine (growth, puberty, and adrenal insufficiency), and gastrointestinal (including nutrition and dysphagia) management.
667 citations
TL;DR: The field has reached the stage at which the results in mdx mice can be validated and scaled-up in symptomatic large animals, and the canine DMD (cDMD) model will be excellent for these studies.
Abstract: Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disorder. It is caused by loss-of-function mutations in the dystrophin gene. Currently, there is no cure. A highly promising therapeutic strategy is to replace or repair the defective dystrophin gene by gene therapy. Numerous animal models of DMD have been developed over the last 30 years, ranging from invertebrate to large mammalian models. mdx mice are the most commonly employed models in DMD research and have been used to lay the groundwork for DMD gene therapy. After ~30 years of development, the field has reached the stage at which the results in mdx mice can be validated and scaled-up in symptomatic large animals. The canine DMD (cDMD) model will be excellent for these studies. In this article, we review the animal models for DMD, the pros and cons of each model system, and the history and progress of preclinical DMD gene therapy research in the animal models. We also discuss the current and emerging challenges in this field and ways to address these challenges using animal models, in particular cDMD dogs.
392 citations
Cites background from "THE 6‐minute walk test and other en..."
...Clinical features of DMD Large-scale population studies have outlined the natural disease progression in affected humans (Table 1) (Bushby and Connor, 2011; Henricson et al., 2013; Magri et al., 2011; McDonald et al., 2013a; McDonald et al., 2013b; Spurney et al., 2014)....
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...Between ages 5 and 8, symptoms are often stabilized or even slightly improved (known as the ‘honeymoon’ period) in the absence of any treatment (Bushby and Connor, 2011; McDonald et al., 2013a; McDonald et al., 2010)....
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TL;DR: In this article, the authors evaluated the long-term efficacy and safety of eteplirsen, a phosphorodiamidate morpholino oligomer designed to skip exon 51 in patients with Duchenne muscular dystrophy.
Abstract: Objective
To continue evaluation of the long-term efficacy and safety of eteplirsen, a phosphorodiamidate morpholino oligomer designed to skip DMD exon 51 in patients with Duchenne muscular dystrophy (DMD). Three-year progression of eteplirsen-treated patients was compared to matched historical controls (HC).
Methods
Ambulatory DMD patients who were ≥7 years old and amenable to exon 51 skipping were randomized to eteplirsen (30/50mg/kg) or placebo for 24 weeks. Thereafter, all received eteplirsen on an open-label basis. The primary functional assessment in this study was the 6-Minute Walk Test (6MWT). Respiratory muscle function was assessed by pulmonary function testing (PFT). Longitudinal natural history data were used for comparative analysis of 6MWT performance at baseline and months 12, 24, and 36. Patients were matched to the eteplirsen group based on age, corticosteroid use, and genotype.
Results
At 36 months, eteplirsen-treated patients (n = 12) demonstrated a statistically significant advantage of 151m (p < 0.01) on 6MWT and experienced a lower incidence of loss of ambulation in comparison to matched HC (n = 13) amenable to exon 51 skipping. PFT results remained relatively stable in eteplirsen-treated patients. Eteplirsen was well tolerated. Analysis of HC confirmed the previously observed change in disease trajectory at age 7 years, and more severe progression was observed in patients with mutations amenable to exon skipping than in those not amenable. The subset of patients amenable to exon 51 skipping showed a more severe disease course than those amenable to any exon skipping.
Interpretation
Over 3 years of follow-up, eteplirsen-treated patients showed a slower rate of decline in ambulation assessed by 6MWT compared to untreated matched HC. Ann Neurol 2016;79:257–271
383 citations
Newcastle University1, Children's Hospital of Philadelphia2, Cincinnati Children's Hospital Medical Center3, University of Kansas4, University of Western Ontario5, University of Milan6, Washington University in St. Louis7, University of Minnesota8, Nationwide Children's Hospital9, Katholieke Universiteit Leuven10, University of Sydney11, Catholic University of the Sacred Heart12, Oregon Health & Science University13, Royal Children's Hospital14, University of Gothenburg15, University of Iowa16, University of Pennsylvania17, Boston Children's Hospital18, University of Utah19
TL;DR: As the first investigational new drug targeting the underlying cause of nm‐dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need.
Abstract: Introduction: Dystrophinopathy is a rare, severe muscle disorder, and nonsense mutations are found in 13% of cases. Ataluren was developed to enable ribosomal readthrough of premature stop codons in nonsense mutation (nm) genetic disorders. Methods: Randomized, double-blind, placebo-controlled study; males ≥5 years with nm-dystrophinopathy received study drug orally 3 times daily, ataluren 10, 10, 20 mg/kg (N = 57); ataluren 20, 20, 40 mg/kg (N = 60); or placebo (N = 57) for 48 weeks. The primary endpoint was change in 6-Minute Walk Distance (6MWD) at Week 48. Results: Ataluren was generally well tolerated. The primary endpoint favored ataluren 10, 10, 20 mg/kg versus placebo; the week 48 6MWD Δ = 31.3 meters, post hoc P = 0.056. Secondary endpoints (timed function tests) showed meaningful differences between ataluren 10, 10, 20 mg/kg, and placebo. Conclusions: As the first investigational new drug targeting the underlying cause of nm-dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need. Muscle Nerve 50: 477–487, 2014
345 citations
Cites background or methods from "THE 6‐minute walk test and other en..."
...7 meters difference in 6MWD should be considered the minimal clinically important difference (MCID), and it is clinically relevant for nmDMD patients.(26) Although not statistically significant, patients treated with ataluren 40 mg/kg/day demonstrated a 31....
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...6MWD, whereas a >8-s stair climb predicts greater likelihood of loss of ambulation over 1 year.(26) The methods used by patients to perform these tests...
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...Completion of this trial has provided a better understanding of the natural history of DMD using the 6MWT and has established the 6MWT as a validated primary endpoint in DMD clinical trials; in addition, the data from this trial have helped to identify the best secondary endpoints in DMD trials and lay the clinical trial groundwork for future therapies for this disease.(26)...
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...and, like the 6MWT, are predictive of the time for a patient to become nonambulatory.(26) Natural history data from the Cooperative International Neuromus-...
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University of California, Davis1, University of Western Ontario2, Children's Hospital of Philadelphia3, Nemours Foundation4, Nationwide Children's Hospital5, Katholieke Universiteit Leuven6, Rush University Medical Center7, Medical University of Warsaw8, University of Freiburg9, University College London10, University of Barcelona11, University of Duisburg-Essen12, Karolinska University Hospital13, University of California, Los Angeles14, University of Florida15, Boston Children's Hospital16, Instituto Politécnico Nacional17, National Institute for Health Research18, Cincinnati Children's Hospital Medical Center19, The Catholic University of America20, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico21, Vita-Salute San Raffaele University22
TL;DR: Ataluren was generally well tolerated and most treatment-emergent adverse events were mild to moderate in severity, and there was a significant effect of ataluren in the prespecified subgroup of patients in the intention-to-treat population.
330 citations
References
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TL;DR: The endothelin-receptor antagonist bosentan is beneficial in patients with pulmonary arterial hypertension and is well tolerated at a dose of 125 mg twice daily.
Abstract: Methods In this double-blind, placebo-controlled study, we randomly assigned 213 patients with pulmonary arterial hypertension (primary or associated with connective-tissue disease) to receive placebo or to receive 62.5 mg of bosentan twice daily for 4 weeks followed by either of two doses of bosentan (125 or 250 mg twice daily) for a minimum of 12 weeks. The primary end point was the degree of change in exercise capacity. Secondary end points included the change in the Borg dyspnea index, the change in the World Health Organization (WHO) functional class, and the time to clinical worsening. Results At week 16, patients treated with bosentan had an improved six-minute walking distance; the mean difference between the placebo group and the combined bosentan groups was 44 m (95 percent confidence interval, 21 to 67; P<0.001). Bosentan also improved the Borg dyspnea index and WHO functional class and increased the time to clinical worsening. Conclusions The endothelin-receptor antagonist bosentan is beneficial in patients with pulmonary arterial hypertension and is well tolerated at a dose of 125 mg twice daily. Endothelin-receptor antagonism with oral bosentan is an effective approach to therapy for pulmonary arterial hypertension. (N Engl J Med
2,443 citations
Newcastle University1, Children's Hospital of Philadelphia2, Case Western Reserve University3, Duke University4, Veterans Health Administration5, Cincinnati Children's Hospital Medical Center6, University of California, Davis7, University of Rochester8, Baylor College of Medicine9, Boston Children's Hospital10, Centers for Disease Control and Prevention11
TL;DR: These recommendations provide a framework for recognising the multisystem primary manifestations and secondary complications of DMD and for providing coordinated multidisciplinary care.
Abstract: Duchenne muscular dystrophy (DMD) is a severe, progressive disease that aff ects 1 in 3600–6000 live male births. Although guidelines are available for various aspects of DMD, comprehensive clinical care recommendations do not exist. The US Centers for Disease Control and Prevention selected 84 clinicians to develop care recommendations using the RAND Corporation–University of California Los Angeles Appropriateness Method. The DMD Care Considerations Working Group evaluated assessments and interventions used in the management of diagnostics, gastroenterology and nutrition, rehabilitation, and neuromuscular, psychosocial, cardiovascular, respiratory, orthopaedic, and surgical aspects of DMD. These recommendations, presented in two parts, are intended for the wide range of practitioners who care for individuals with DMD. They provide a framework for recognising the multisystem primary manifestations and secondary complications of DMD and for providing coordinated multidisciplinary care. In part 1 of this Review, we describe the methods used to generate the recommendations, and the overall perspective on care, pharmacological treatment, and psychosocial management.
1,664 citations
"THE 6‐minute walk test and other en..." refers background in this paper
...Muscle Nerve 48: 343–356, 2013 Duchenne muscular dystrophy (DMD) is a disabling and life-threatening X-linked genetic disorder caused by defects in the gene for dystrophin that results in a progressive loss of functional muscle fibers and weakness with stereotypic functional consequences affecting mobility, progressive musculoskeletal deformities, upper limb impairment, impaired airway clearance and ventilation, cardiomyopathy, and premature death.(1,2) The past several years have seen increased interest by biopharmaceutical companies in conducting ground-breaking research and development into novel treatment agents for DMD....
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TL;DR: The selectivity of PTC124 for premature termination codons, its well characterized activity profile, oral bioavailability and pharmacological properties indicate that this drug may have broad clinical potential for the treatment of a large group of genetic disorders with limited or no therapeutic options.
Abstract: Nonsense mutations promote premature translational termination and cause anywhere from 5-70% of the individual cases of most inherited diseases. Studies on nonsense-mediated cystic fibrosis have indicated that boosting specific protein synthesis from <1% to as little as 5% of normal levels may greatly reduce the severity or eliminate the principal manifestations of disease. To address the need for a drug capable of suppressing premature termination, we identified PTC124-a new chemical entity that selectively induces ribosomal readthrough of premature but not normal termination codons. PTC124 activity, optimized using nonsense-containing reporters, promoted dystrophin production in primary muscle cells from humans and mdx mice expressing dystrophin nonsense alleles, and rescued striated muscle function in mdx mice within 2-8 weeks of drug exposure. PTC124 was well tolerated in animals at plasma exposures substantially in excess of those required for nonsense suppression. The selectivity of PTC124 for premature termination codons, its well characterized activity profile, oral bioavailability and pharmacological properties indicate that this drug may have broad clinical potential for the treatment of a large group of genetic disorders with limited or no therapeutic options.
1,085 citations
TL;DR: A tremendous heterogeneity of severity among males with Becker's muscular dystrophy is suggested, with mean intellectual and neuropsychologic function within normal limits, but with a large variability in intelligence quotient scores.
Abstract: One hundred and sixty-two patients with Duchenne muscular dystrophy (DMD) were followed over a 10-yr period to provide a profile of impairment and disability. The median height and weight of DMD boys were normally distributed before ages 9-10, but during the second decade height was markedly reduced, and weight was no longer normally distributed. Younger boys gained more weight than normals, whereas older individuals actually showed weight loss. Manual muscle test (MMT) measurements showed loss of strength in a fairly linear fashion from ages 5-13 yr, -0.25 MMT units per year. Upper extremity muscles were stronger than lower extremity muscles, proximal muscle groups were weaker than distal muscle groups, and extensor muscles were weaker than flexor muscles. There was no side dominance. There was a change in the rate of strength loss at 14-15 yr, and the decline slowed to only -0.06 MMT units per year. Although MMT and quantitative strength measurement profiles were similar, the latter were far more sensitive. In general, by the time strength declined to MMT grade 4, isometrically measured strength was 40-50% of normal control values. Joint contractures were rare before age 9, increased in frequency and severity with age, and were present in most individuals older than 13. Lower extremity contractures were strongly related to onset of wheelchair reliance, but there was no association between muscle imbalance around a joint. The prevalence of scoliosis increased between ages 11 and 16, with about 50% of the boys acquiring scoliosis between ages 12 and 15, corresponding to the onset of the adolescent growth spurt. Wheelchair reliance and scoliosis were both age-related. Percent predicted forced vital capacity declined at different yearly rates: ages 7-10, -0.3%; ages 10-20, -8.5%; after age 20, -6.2%. There was a direct relationship between percent predicted FVC and MMT scores. Decreased airway pressures, especially maximal expiratory pressure, appeared earlier than reductions in FVC but followed the same pattern. Thirty percent of the DMD boys had a history of respiratory complications, and the frequency increased with age. Spine deformity did not have a significant additive effect on the age-related decrement in pulmonary function. There was a high occurrence (79%) of abnormal electrocardiograms with age-related progression of some abnormalities, but only 30% of the patients had a history of cardiovascular complications. Functional level grades and timed motor performance measurements had a nonlinear relationship with strength and age.(ABSTRACT TRUNCATED AT 400 WORDS)
1,078 citations
Newcastle University1, Children's Hospital of Philadelphia2, Case Western Reserve University3, Duke University4, Veterans Health Administration5, Cincinnati Children's Hospital Medical Center6, University of California, Davis7, University of Rochester8, Baylor College of Medicine9, Boston Children's Hospital10, Centers for Disease Control and Prevention11
TL;DR: A comprehensive set of DMD care recommendations for management of rehabilitation, orthopaedic, respiratory, cardiovascular, gastroenterology/nutrition, and pain issues, as well as general surgical and emergency-room precautions are presented.
Abstract: Optimum management of Duchenne muscular dystrophy (DMD) requires a multidisciplinary approach that focuses on anticipatory and preventive measures as well as active interventions to address the primary and secondary aspects of the disorder. Implementing comprehensive management strategies can favourably alter the natural history of the disease and improve function, quality of life, and longevity. Standardised care can also facilitate planning for multicentre trials and help with the identification of areas in which care can be improved. Here, we present a comprehensive set of DMD care recommendations for management of rehabilitation, orthopaedic, respiratory, cardiovascular, gastroenterology/nutrition, and pain issues, as well as general surgical and emergency-room precautions. Together with part 1 of this Review, which focuses on diagnosis, pharmacological treatment, and psychosocial care, these recommendations allow diagnosis and management to occur in a coordinated multidisciplinary fashion.
997 citations
"THE 6‐minute walk test and other en..." refers background in this paper
...Muscle Nerve 48: 343–356, 2013 Duchenne muscular dystrophy (DMD) is a disabling and life-threatening X-linked genetic disorder caused by defects in the gene for dystrophin that results in a progressive loss of functional muscle fibers and weakness with stereotypic functional consequences affecting mobility, progressive musculoskeletal deformities, upper limb impairment, impaired airway clearance and ventilation, cardiomyopathy, and premature death.(1,2) The past several years have seen increased interest by biopharmaceutical companies in conducting ground-breaking research and development into novel treatment agents for DMD....
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